The proposed research will explore mechanisms of transmission of CHD risk factors and the interrelationships of these factors with behavioral and psychosocial variables in two potentially valuable and uniquely comprehensive data sets: (1) A population of 268 pairs of adult twins (127 MZ and 141 DZ residing in California, who formed one of the cohorts in the NHLBI study of twins in 1971-1973. (2) A population of 900 subjects in 220 nuclear families, the fathers of which participated in the Western Collaborative Group Study (WCGS) in 1960-1969. These subjects were studied for all accepted risk factors for coronary heart disease, including Type A behavior pattern (TABP). The current investigaton proposes to use classical methods as well as a new statistical methodology--SEDA (Structural Exploratory Data Analysis)--to determine the nature of familial resemblance, mode of transmission, and gene-environment interaction of major CHD risk factors. Special emphasis will be given to the study of the familial component of TABP, its behavioral and psychosocial correlates, and its relationship to other established CHD risk factors. It is believed that the findings of this study will provide uniquely new knowledge in this field where such is needed. The potential significance of this research is strengthened by the fact that both the WCGS twin cohort are currently undergoing an extensive follow-up that provides additional data on CHD endpoints. Specifically, the proposed study will enrich our knowledge of the role of genetic and cultural factors in the transmission of CHD as well as of their value for predicting initial and recurring manifestations.